202 Mr. G. Brook on the Bate of Development 



the same colour, terminating beneath second median nervule, 

 where it is narrowest ; the outer margin also darker brown, 

 with the apex and extreme margin pale violaceous. Posterior 

 wings with the basal fourth dark chocolate-brown, with a 

 narrow outer violaceous margin ; a small chocolate-brown 

 spot margined with violaceous above the submedian nervure, 

 a narrow waved central violet-margined fascia crossing disk, 

 strongly fractured at end of cell, and then more narrowly con- 

 tinued to internal nervure ; this is followed by a short and 

 somewhat broken fascia, commencing at lower subcostal nervule 

 and narrowly terminating at lower median nervule, the whole 

 outer margin broadly infuscated, the apex and extreme margin 

 pale violaceous. Body and legs more or less concolorous 

 with wings. 



Exp. wings, $ 51 millira. 



Hc^. Perak {Kilnstler^ Calcutta Mus.). 



This beautiful species, of which I have only seen two male 

 specimens, belongs to the Apidanus section of the genus. 



XXVII. — On the Rate of Development of the Common Shore- 

 Crab (Carcinus m^enas). By George Brook, F.L.S. 



[Plate VIL] 



For over two years now I have been carrying on a series of 

 experiments in my aquarium, with the object of throwing 

 some light on the rate of development of Carcinus mcenas. For 

 this purpose from twenty to thirty specimens have been kept 

 and isolated, and every cast shell has been carefully preserved 

 and labelled. I should have liked, if possible, to have traced 

 this development from the newly hatched Zoea, but although I 

 have had thousands of Zoea3 hatched in confinement I never 

 yet succeeded in rearing any past the second or third moult. 

 In August last, however, I collected a few of the Megalopa 

 stage of Carcinus at Redcar, which at the next moult assumed 

 the ordinary adult form of the Brachyuran. As soon as this 

 stage was reached there was no difficulty in feeding them ; 

 and I am now able to combine twelve months' observations 

 on this gathering with the material I had obtained from other 

 specimens. 



Mr. C. Spence Bate, in his paper on the " Development of 

 Decapod Crustacea " (Phil. Trans. 1858), gives a full account 

 of the changes gone through by the young Carcinus from 

 leaving the &^^ to assuming the adult form. He says 

 (p. 597) : — " Having pursued tlie course of development 

 from the larva to the mature form of the Brachyuran decapod 



